Laser catheters and laser delivery systems in general have wide range of applications in the medical field. Such systems may be used to deliver laser energy to desired sites of a patient's anatomy, and may be particularly suitable for delivering laser energy to locations within a patient's body that allow for minimally invasive treatment of a variety of indications using a variety of treatment modalities. Examples of some laser treatment modalities include heating tissue, stimulating tissue, drug activation within a patient's tissue and ablation of tissue.
Laser catheters currently approved for clearing blockages in human arteries may use single or more commonly multiple bundle pure silica optical fibers for indications using ultraviolet laser pulse durations greater than about 50 nsec, usually greater than about 100 nsec to prevent damage to small diameter optical fibers used in multiple optical fiber delivery catheter designs. Typically, optical fiber elements having a transmissive core with a transverse dimension or diameter of about 50 microns to about 100 microns may be used in ablation catheters having multiple optical fiber bundles.
In some cases, single large diameter optical fibers having a transmissive core with a transverse dimension or diameter greater than about 130 microns may be too stiff or resistant to longitudinal bending for use in the arteries of a patient, particularly the coronary arteries of a human patient. Therefore, multiple optical fiber bundles using optical fibers having a smaller transverse dimension or diameter may be used to improve flexibility of the catheter while maintaining a constant transmissive core area. These optical fiber laser catheters may be up to 12 feet long and contain from about 50 optical fibers to about 300 optical fibers depending on the cross sectional size of the catheter ablation tip. These pure silica optical fibers are expensive and have a low percentage of cutting area due to the clad and buffer used on the outside of the light conducting or transmissive core as well as a low density packing factor for the multiple fibers having a circular transverse cross section disposed in a bundle.
Another way for delivering laser energy to a remote site includes the use of a fluid core waveguide. Existing commercial fluid core waveguides having a transmissive fluid core may typically have an inner diameter of about 2 mm to about 5 mm and a length of about 1 m to about 5 m and have useful light transmission from the ultraviolet to the visible wavelengths at greater than 50% transmission in some cases. Such designs may be robust for repeated use but are large in size and may not be scalable to a smaller more flexible design for use as a disposable catheter in tortuous vessels such as a patient's vasculature. Such designs may also not be adaptable to smaller more flexible embodiments to be used with a high pulse power and high pulse energy laser such as the ultraviolet excimer laser, particularly the 308 nm XeCl excimer. Also, many of the previously disclosed fluids used for the transmissive core of these fluid core waveguides may not be suitably biocompatible for use inside the human body.
What has been needed is a fluid core waveguide based ablation catheter that is small and flexible enough to navigate a patient's vasculature, uses biocompatible fluids, and is economical to manufacture. What has also been needed is a fluid core waveguide based ablation catheter that can be efficiently packaged and sterilized and maintain clinical integrity during a useful shelf life after shipment to an end user.